1. Field of the Invention
This invention relates to a die bonding apparatus for electrically connecting the electrodes on the die or semiconductor chip with the corresponding electrodes or leads of the package body etc. by heating under pressure, and more particularly to a face bonding apparatus for establishing electrical connection of a plurality of electrodes on one side of a semiconductor chip with a plurality of electrodes on the package body by pressing these elements against each other under the application of heat. More specifically, this invention relates to a die bonding apparatus suitable for mounting or packaging the semiconductor chip based on the TAB (tape automated bonding) method.
2. Description of the Prior Art
FIG. 11 shows an example of a well known type of die bonding apparatus having a pressing and heating tool 1 that is provided as one of pinching and pressing means and which vertically moves along guide bars 7 while being supported thereon by bearings 6, the guide bars 7 standing vertically and being fixed on a base 5 provided as the other one of the pinching and pressing means. When this pressing and heating tool 1 is moved down along the guide bars 7, it presses a silicon chip 2 at its lower surface 1a formed as a pinching and pressing surface, as indicated by the broken line in the drawing. The opposite ends of the silicon chip 2 are placed on the bumps 3 at the inner ends of two wiring members 4 disposed on a surface 5a of the base 5 which serves as a pinching and pressing surface. The wiring members 4 and the silicon chip 2 are electrically connected in this manner.
If, in this type of conventional bonding apparatus, the lower surface 1a of the pressing and heating tool 1 and the upper surface (opposed surface) 2a of the silicon chip 2 are not parallel with each other as shown in FIG. 12, the pressure applied by the tool 1 on the chip 2 is not uniformly distributed over the chip 2, resulting in the variation in the strength of the connection between each of the wiring members 4 and the corresponding electrode part on the silicon chip 2. Moreover, if the two opposed surfaces 1a, 2a are at such states where the deviation from parallelism therebetween is significant, a gap 9 may be formed between the silicon chip 2 and the pressing and heating tool 1 so that there is a possibility of failure in the contact between the silicon chip 2 and the connecting bumps 3 after these members have been pressed.
The deviation from the parallelism between the lower surface 1a of the tool 1 and the opposed surface 2a of the chip 2 may be increased not only when, as shown in FIG. 12, the sizes (heights) of the left and right bumps 3 as a whole are different from each other so that the silicon chip 2 is inclined on the bumps 3 (normally 20 to 30 .mu. in height in the case of a 80 .mu. square), but also when the thickness of the chip 2 is not uniform or when a foreign particle enters between the chip and the wiring members. Also it may be increased by an dimensional error on the side of the tool 1 which will result in an inclination of the lower surface 1a of the tool 1 relative to a virtual plane perpendicular to that of the translation of the tool 1.
Japanese Patent Application Laid-Open No. 37842/1982 discloses a die bonding apparatus, for the purpose of eliminating these problems, which has a mechanism constituted by spherical sliding portions whereby the plane defined by the bumps on a semiconductor chip is adjusted to be parallel with the surface of the tool.
The apparatus disclosed in Japanese Patent Laid-Open No. 37842/1982 is constituted as shown in FIG. 13. A pressing and heating tool 101 constituting one of the pinching and pressing means is moved in the direction indicated by the reference numeral 111 down onto a semiconductor chip 102 so as to press patterns 107 formed on tapes 108 against bumps 103 formed on the surface of the semiconductor chip 102. If at this time the bumps 103 are not of the same heights to define a plane parallel with the chip surface, in other words, the lower surface (pinching and pressing surface) 101a of the tool 101 is not parallel with the surface of the semiconductor chip 102, a ball 105 slidingly moves along the spherical contact surface 112 of a ball receiving member 106 and swings so that the pressure applied to each of the patterns 107 and to each of the bumps 103 is equalized.
After the plane defined by the bumps 103 have been made parallel with the lower surface 101a of the tool 101 by the rotational displacement of the ball 105 and after the patterns 107 and the bumps 103 are pressed together, the tool 101 is heated, thereby connecting the patterns 107 to the bumps 103. Incidentally, the apparatus has an heat insulation member 104 provided as the other one of the pinching and pressing means and a base 110.
The apparatus shown in FIG. 13 has the following problems:
(1) Since the center A of the sphere of the spherical seat 112 is remote from the lower surface 101a of the tool 101 or the surfaces of the chip 102, there are displacements of the bumps 103 not only in the vertical direction but also in the horizontal direction when the ball 105 is rotationally displaced about the center A. Therefore there is a possibility of failure in the electrical connection between the bumps 103 and the associated leads 107.
(2) a When the spherical surface 112 is formed by as a sliding surface, the friction between the spherical sliding surfaces would become substantial, which would be inappropriate for correcting the delicate uneven abutment caused by a relatively small deviation from the parallelism between the lower surface 101a of the tool 101 and upper surface defined by the conductors 107 or bumps 103.
b If the spherical seat 112 is designed to provide rolling contact, the mass of the moving parts is increased so large that this mechanism cannot always effect suitable aligning operation because of the increased inertia when the bonding apparatus is to be operated at high speed.
c In any case, the number of parts or components for the apparatus is increased, resulting in a high production cost.
(3) There is a possibility that the ball 105 is freely turned about a vertical line including the point A relative to the ball receiver 106. It is therefore difficult to position the chip 102 accurately.